That would be an unlocked chip, but generally they aren't better overclockers from the rest of the retail chips - in fact many times they're worse simply because they're early production samples. Aside from having an unlocked multiplier they're not stellar performers. Also be aware that ES chips are always the property of Intel and are not to be sold, period. If Intel corporate security catches the transaction they'll hunt you down and force you to return the cpu. They don't play around - in fact they were about to call the local sheriffs department to seize one from me.